(1) Field of the Invention
The present invention relates to a voice coil insertion jig used in manufacturing speakers that are incorporated in various acoustic appliances, a method of manufacturing a speaker using this jig, and a speaker manufactured by using this jig.
(2) Description of Related Art
The prior art is explained by referring to FIGS. 3 to 5. FIG. 3 is a sectional view of a speaker, FIG. 4 is a perspective exploded view of a voice coil assembling jig used when assembling the speaker, and FIG. 5 is a sectional view illustrating the assembling process of the voice coil.
A structure of a speaker is described in FIG. 3. Magnetic circuit 1 is composed of a lower plate 1a having a center pole 1b, a magnet 1c coupled on a lower plate 1a, and an upper plate 1d coupled on magnet 1c. Magnetic circuit 1 has a magnetic gap 1e between upper plate 1d and center pole 1b. A frame 2 is coupled to upper plate 1d. A diaphragm 3 is coupled to frame 2 by way of an edge 3a formed on an outer circumference of diaphragm 3. A voice coil 4 is composed of a coil 4a and a bobbin 4b. Coil 4a is inserted in magnetic gap 1e, and an internal circumference of diaphragm 3 is coupled to a specified position of bobbin 4b. An outer circumference of damper 5 is coupled to frame 4, and an inner circumference of damper 5 is coupled to bobbin 4b. In this constitution, voice coil 4 is supported movably up and down.
In the manufacturing process of such a speaker, what requires the highest precision is the inserting process of voice coil 4 into magnetic gap 1e. 
A conventional voice coil insertion jig disclosed in Japanese Laid-open Utility Model No. 57-160292 is explained by referring to FIGS. 4 and 5. The conventional voice coil insertion jig is composed of a jig main body 11, a gauge tube 12, a slit 13, and a spring 14.
Spring 14 is assembled into an inside of jig main body 11, and generates a force for opening slit 13. The insertion jig is inserted into bobbin 4b while closing slit 13, and after positioning, voice coil 4 is fixed by the pressure of spring 14. Together with the jig, voice coil 4 is inserted into center pole 1b of magnetic circuit 1. That is, voice coil 4 is inserted into magnetic gap 1e. At this time, depending on the material thickness of gauge tube 12, the position of voice coil 4 in the radial direction is defined. In this state, frame 2 is adhered and coupled to magnetic circuit 1. (Frame 2 may be first adhered and coupled to magnetic circuit 1.) After adhering damper 5 and diaphragm 3 to frame 2 and bobbin 4b, the insertion jig is pulled out of the speaker. Finally, dust cap 6 is adhered and coupled to diaphragm 3, and the speaker is manufactured.
Thus, in the speaker manufacturing process, the voice coil insertion jig is required to have a high precision for positioning voice coil 4.
As the appliance is reduced in size recently, a speaker of small size and high efficiency is demanded. For this purpose, magnetic gap 1e is required to be much narrower.